# Series grouping

- Same current flows through each resistance but potential difference distributes in the ratio of resistance, i.e.,
*V*∝*R***Fig. 13** - Equivalent resistance is greater than the maximum value of resistance in the combination, i.e.,
*R*=_{eq}*R*_{1}+*R*_{2}+*R*_{3.} - If
*n*identical resistance are connected in series*R*=_{eq}*nR*and potential difference across each resistance*V*’ =*V*/*n*.

# Parallel grouping

- Same potential difference appeared across each resistance but current distributes in the reverse ratio of their resistance, i.e.,
*i*∝ 1/*R.***Fig. 14** - Equivalent resistance is given by
- If two resistances in parallel,
- Current through any resistance,
*i*’ = required current (branch current),*i*= main current and**Fig. 15** - In
*n*identical resistance are connected in parallel*R*=_{eq}*R*/*n*and current through each resistance*i*’ =*i*/*n.*

*Notes:*- If
*n*identical resistances are first connected in series and then in parallel, the ratio of the equivalent resistance is given by . - If equivalent resistance of
*R*_{1}and*R*_{2}in series and parallel be*R*and_{s}*R*, respectively, then_{p}*R*is cut in*n*equal parts and then these parts are collected to form a bundle, then equivalent resistance of combination will be*R*/*n*^{2}.